Volume control system



Feb. 7, 1933. E. R. HENTSCHEL VOLUME CONTROL SYSTEM Filed 001;. 23, 1930 m hhi u o 6 0 on INVENTOR ATTORNEY v miv Patented Feb. 7, 1933 UNITED STATES PATENT OFFICE ERNEST R. HEN'I'SCEEL, OF WASHINGTON, DISTRICT OF COLUMBIA; JOHN OLSON, AD-

MINISTBATOR'OF SAID. ERNEST R. HENTSCHEL, DECEASED, ASSIGNOB TO WIRED RADIO, INC., 0]! NEW YORK, N. Y., A CORPORATION OF DELAWARE VOLUME CONTROL SYSTEM.

Application filed October 23, 1980. i Serial No. 490,789.

My invention relates broadly to volume control systems for radio receivers and more particularly to a circuit arrangement for controlling the impedance of the antenna path in a radio broadcast receiver according to the amplitude of the incoming signaling energy.

One of the objects of my invention is to provide an automatic volume control circuit for radio receivers wherein the impedance of the antenna path may be directly controlled according to the amplitude of the incoming signaling energy for eliminating the effect of fading upon the operation of the radio broadcast receiver.

Another object of my invention is to provide an arrangement of electron tube circuit in the antenna path of a radio broadcast receiver wherein the impedance of the antenna path is varied according to the amplitude of the incoming signaling energy.

A further object of my invention is to'provide an arrangement of electron tube circuit in the antenna path of a radio broadcast receiver having means for excluding radio frequency currents from the power circuits of the electron tubes while establishing a path to ground through the cathode-anode impedance of an electron tube, the said path being variable in its effective value according to the amplitude of the incoming signaling energy, whereby the volume of reproduced sound is ralaintained at substantially uniform amplitu e.

Other and further objects of my invention reside in the circuit arrangement for a radio broadcast receiver as set forth more fully in the specification hereinafter following and illustrated in the accompanying drawing, wherein:

Figure 1 diagrammatically shows the application of the circuit arrangement of my invention to a radio broadcast receiver; and Fig. 2 graphically illustrates the characteristics of the circuit arrangement of my invention.

Referring to the drawing in detail, reference character 1 designates the first stage of radio frequency amplification coupled to the second stage of radio frequency amplification designated at 2 which is in turn coupled to the detector tube 3, the output circuit of which vis coupled to the audio frequency amplifier indicated by electron tube 4. Reference character-6 indicates a radio frequenc rectifier tube of the three element type whic is energized from the plate circuit of tube 2 through primary winding which is coupled to tuned secondary winding 16 which in turn is connected to the grid of tube 6. The grid of tube 6 is biased by adjusting tap 29 on potentiometer 51 so that there is no current in the plate until the amplitude of energy supplied to the detector exceeds the desired value when pulses of radio frequency current flow in the plate circuit. Condenser 18 is a radio frequency by-pass condenser which by-passes the radio frequency energy to ground. Reactances 21 and 23, in combination with condensers 20, 22 and 24, constitute an audio frequency filter system, the purpose of which is to filter out the audio frequency components of the plate current so as to supply steady current through resistance 25 when tube 6 is functioning.

The potential difierence across resistance 25 is used to change the negativebias on'the grid of tube 5 which is an auxiliary tube placed in series in the antenna ground circuit of the broadcast receiver. The normal grid bias of this tube is governed by adjusting taps 32 and 33 on potentiometer 51. When there is no current in resistance 25 then the grid bias on tube 5 is equal to the potential difference between taps 32 and 33, but when current flows in resistance 25 then the potential difference across the resistance is added to the steady negative bias on the grid impedance of tube 5. There is a steady direct i of tube 5 and increases the impedance of this i current voltage applied to the plate of tube 5 through tap 34 on potentiometer 51 in order that the impedance of this tube may be caused tobvary by changing the grid biasing of this tu e.

In Fig. 2, I have illustrated diagrammatically the conditions existing in tube 5. Plate current I has been plotted as ordinates and plate voltage Ep has been plotted as abscissa. Numeral 44 represents the plate current voltage curve with a given bias on the grid. Line 50 on the abscissa represents the fixed voltage applied to the plate, and on both sides of this line is shown the radio frequency electromotive force illustrated by curve 49 for conditions existing when curve 44 represents plate current. Curve 46 represents the radio frequency variations in plate current, while line 53 represents the steadily flowing plate cur rent. Curve 45 rep-resents the plate current versus plate voltage for the condition of a higher negative bias on the grid. Curve 48 represents a value of radio frequency electromotive force in the antenna circuit at this time, and curve 47 represents the radio frequency plate current, and line 54 represents the steady value of plate current.

As can be seen from the drawing, when the grid bias is high, and the tube impedance also high, that a larger value of signal in the antenna circuit will not produce an increase in the radio frequency energy in primary inductance 10 due to the change in slope of the characteristic, and therefore by correct adjustment of constants the input energy to the receiver may be maintained constant.

The radio frequency amplifier is coupled to the antenna-ground system 60 through secondary winding 40 which is inductively related to primary inductance 10 in the antenna-ground circuit. Secondary winding 40 is tuned by condenser 41. The radio frequency amplifier stage 1 is coupled through transformer 42 having a secondary winding tuned by condenser 43 with the input of the electron tube 2. The circuit leading from the radio frequency amplifier system 1-2 extends to the detector 3 through the coupling circuit 11 constituted by primary winding 12 in series with primary winding 15 and secondary winding 13 coupled with primary winding 12 and tuned by condenser 14. The plate potential for the electron tubes constituting the radio frequency amplifier stages is obtained through tap connection 17 on potentiometer 51. The grid potentials for the audio frequency amplifier stages 3 and 4 are obtained through tap connections 19 and 26 respectively. The grid bias for the electron tubes constituting the radio frequency amplifierstages is obtained through tap connection 27 on potentiometer 51. The sound reproducer is shown at 30 connected in the output circuit of the final stage of power amplification. Energy for operating the receiver is obtained from the alternating current supply line indicated at 35 and is delivered through transformer 36 to the rectifier system 37 which in turn connects to the filter circuit 38 which delivers rectified alternating current to the potentiometer 51. The cathodes for the several electron tubes are supplied with alternating current in winding 39 of power transformer 36.

While I have described my invention in one of its preferred embodiments, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended other than are imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a volume control system for radio receivers, a radio frequency amplifier, a detector, an audio frequency amplifier, a sound reproducer, a radio frequency energy collecting circuit connected with the input of said radio frequency amplifier, an electron tube including a plurality of electrodes connected in said radio frequency energy collecting circuit for establishing an electron discharge path in series with said radio frequency energy collecting circuit, and means controlled by the amplitude of the signaling current delivered by said radio frequency amplifier for controlling the effective impedance of said electron discharge path in said radio frequency energy collecting circuit.

2. In a radio broadcast receiving system, a radio frequency energy collecting circuit, a radio frequency amplifier, a detector, a sound reproducing circuit connected with said detector, an electron tube including a cold electrode and a thermionic electrode connected in series with said radio frequency energy collecting circuit for establishing an electron discharge path in series with said radio frequency energy collecting circuit and means connected with the output of said radio frequency amplifier for variably controlling the conductivity of said electron discharge path in said radio frequency energy collecting circuit according to the amplitude of the incoming signaling energy.

3. In a radio broadcast receiving system. an antenna, a ground connection, a radio frequency amplifier connected therewith, a detector, connected with said radio frequency amplifier, an audio frequency amplifier connected with said detector, a sound reproducing system connected with said audio frequency amplifier, and a circuit extending from the output of said radio frequency amplifier system for regulating the conductivity of the radio frequency energy collecting circuit included between said antenna and' ground connection comprising an auxiliary electron tube having a multiplicity of electrodes, one of said electrodes being con nected to the antenna, and another being connectedto ground for establishing an electron discharge path in series with the antenna and ground, said means operating to vary the electron discharge path between said elec-- detector, a sound reproducing circuit connected with said detector, an independent electron tube circuit having a pair of its electrodes disposed in series with said antenna-ground circuit, and means for controlling the conductivity of the electron discharge between said electrodes for correspondingly controlling the conductivity of said antenna-ground circuit according to the amplitude of the incoming signaling energy.

5. In a radio broadcast receiver, a radio frequency energy absorption structure, an amplifier connected therewith, an electron tube having a plurality of electrodes and having a pair of its electrodes disposed in series with said absorption structure, and a connection between certain of the electrodes in said electron tube with the output of said amplifier for controlling the conductivity of the electron discharge path between said electrodes and regulating the impedance of said absorption structure according to the amplitude of incoming signaling energy.

6. In a radio broadcast receiver, a radio frequency energy absorption structure, an amplifier connected vtherewith, an electron tube having grid, cathode and plate electrodes, said cathode and plate electrodes being disposed in series with the path through i said absorption'structure, and a circuit extending from the output of said amplifier to said grid electrode for controlling the potential thereof and correspondingl controlling the conductivity of the path tl irough said absorption structure in accordance with the amplitude of the incoming signaling energy.

7. In a radio broadcast receiving system, an antenna-ground circuit, an amplifier connected therewith, an electron tube having a grid, cathode and anode, said cathode and anode being disposed in series in said antenna-ground circuit, means for heating said cathode to electron emitting temperature'for establishing a discharge path between said grid and anode, and means connected between the output of said amplifier and said grid for controlling the potential of said grid according to the amplitude of the incoming signaling energy and correspondingly controlling the efl'ective impedance of said antennaground circuit.

8. A volume control system for. radio broadcast receivers comprising a radio frequency energy absorption structure, an amplifier connected therewith, an electron tube having a cathode, a grid, and an anode, said cathode and anode being connectedin series with said radio frequency energy absorption structure, means for impressing positive potential upon said anode, means for impressing negative potentialupon said grid, and a connection between said last mentioned means and the output of said amplifier.

9. A volume control system for radio broadcast receivers comprising a radio fre quency energy absorption structure, an amplifier connected therewith, an electron tube having a cathode, a grid, and an anode, said cathode and anode being connected in series with said radio frequency energy absorption structure, means for impressing positive potential upon said anode, means for impressing negativepotential upon said grid, a connection between said last mentioned means and the output of said amplifier, and means connected in series with said anode and grid for confining the passage of radio frequency currents to the electron discharge path between said cathode and anode.

In testimony whereof I aflix my signature.

ERNEST R. HENTSGHELL 

